The present invention relates to a combustion apparatus including a cyclonic prechamber and to a combustion process, which may be carried out in the combination apparatus. The combustion process and apparatus are especially applicable to gas turbines fired on liquid fuel, including such turbines employed for electric power generation as in the electric utility industry.
Gas turbine combustors operated on liquid fuel are prone to unacceptably high formation of nitrogen oxides (NO.sub.x) from the standpoint of increasingly rigid government standards. Numerous combustors and processes have been proposed wherein the liquid fuel would be prevaporized, i.e. converted to vapor or gaseous form prior to combustion, and the heat for fuel vaporization would be provided by hot air supplied to the combustor. However, in many of the proposed combustors the liquid fuel residence time required for a minimally acceptable extent of prevaporiztion has required an inordinately large prechamber, frequently resulting in autoignition therein of the fuel/air mixture during operation.
It has now been found by practice of the present invention that the problems of NO.sub.x formation and autoignition in combustion of normally liquid fuel can be at least substantially reduced in a simple, efficient manner. The combustion apparatus and process of this invention provide good balance between sufficiently long residence time of liquid fuel in a prechamber or prevaporization zone for effective fuel vaporization therein and sufficiently short residence time of the ignitable mixture of the resulting fuel vapor with hot air as to substantially avoid autoignition in the prechamber and minimize flashback from a downstream combustion chamber over a variety of operating conditions.